[dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and csum forwarding engine

[Ananyev, Konstantin]

Hi lads,

> -----Original Message-----
> From: Olivier MATZ [mailto:olivier.matz at 6wind.com]
> Sent: Wednesday, January 21, 2015 3:25 PM
> To: Liu, Jijiang; Ananyev, Konstantin
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and csum forwarding engine
> 
> Hi,
> 
> On 01/21/2015 04:12 AM, Liu, Jijiang wrote:
> >>>>> Ok, and why it should be our problem?
> >>>>> We have a lot of things done in a different manner then
> >>>>> linux/freebsd kernel drivers, Why now it became a problem?
> >>>>
> >>>> If linux doesn't need an equivalent flag for doing the same thing, it
> >>>> probably means we don't need it either.
> >>>
> >>> Probably yes .... Or probably not.
> >>> Why do we need to guess what was the intention of guys who wrote that
> >> part of linux driver?
> >>
> >> Because the dpdk looks very similar to that part of linux driver.
> >
> > A  guy from Intel  who have already confirmed that the NVGRE is not supported yet in Linux kernel.
> >
> > He said "So far as I know it is not yet supported and I have no information on when it will be."
> 
> I added the support of Ether over GRE, IP over GRE and IP over IP
> tunnels in csumonly to do the test. I ask the csum forward engine
> to calculate inner IP+TCP checksums, and outer IP (case 6 in [1]).
> Here are the results:
> 
> 1/ When I use I40E_TXD_CTX_UDP_TUNNELING:
> - vxlan: all checksums ok
> - eth over gre: all checksums ok
> - ip over gre: not transmitted by hw
> - ip over ip: all checksums wrong (set to 0 by hw)
> 
> 2/ When I use I40E_TXD_CTX_GRE_TUNNELING:
> - vxlan: checksums ok
> - eth over gre: all checksums ok
> - ip over gre: all checksums ok
> - ip over ip: all checksums wrong (set to 0 by hw)
> 
> 3/ When I use 00b:
> - vxlan: all checksums ok
> - eth over gre: all checksums ok
> - ip over gre: all checksums ok
> - ip over ip: checksums wrong (set to 0 by hw)
> 
> All the ip over ip tests do not work yet for an unknown reason.
> There is maybe something wrong in my app or in the driver
> (although the registers looks consistent with the datasheet).
> 
> I think we could use 3/ for all tunnels, because the ipip case
> is supposed to work according to the datasheet, and all other cases
> work too.
> 
> It would allow to remove the UDP_TUNNELING flag from mbuf API.
> 
> I will send a RFC patch that provides the API change and this new
> feature in csum forward engine, with full tests on ixgbe and i40e
> and explanations for all changes.
> 
> Regards,
> Olivier
> 
> [1] http://dpdk.org/ml/archives/dev/2015-January/011127.html

I tried to repeat Olivier test-cases on my box.
Though, I didn't use test-pmd cusmonly and  i40ePMD logic, but filled TCD and TDD mostly from hardcoded values.
That's  what I got:

4 input packets:
a) ETHER/IPv4/UDP/VXLAN/ETHER/IPV4/TCP
b) ETHER/IPv4/GRE/ETHER/IPV4/TCP
c) ETHER/IPv4/GRE/IPV4/TCP
d) ETHER/IPv4/IPV4/TCP

1/ L4TUNT==1(I40E_TXD_CTX_UDP_TUNNELING):
a),b): all checksums ok
c),d): not transmitted by HW.

2/ L4TUNT==2(I40E_TXD_CTX_GRE_TUNNELING):
a) b),c): all checksums ok
d): not transmitted by HW.

3/ L4TUNT==0(UNKNOWN):
a),b),c),d): all checksums ok

So yes, it seems that L4TUNT==0 works perfectly ok for all cases, as long as L4TUNLEN and other TCD values are setup properly.
Which makes me think, that  probably we can do what you suggested: just use L4TUNT=0 for all cases. 
Though as Jijiang said, we waiting for confirmation from FVL guys, that there are no hidden implications with that approach.

Another thing - IPIP seems to work ok by HW.
There is something wrong on our (PMD/test-pmd) side.
I think at least we have to remove the following check:
if (!l2_len) {
                PMD_DRV_LOG(DEBUG, "L2 length set to 0");
                return;
        }
in i40e_txd_enable_checksum().

Konstantin